Hackers Backdoor Nextcloud Servers Through Critical Flaw in Collabora’s Built-in CODE App

Hackers have been exploiting a critical flaw in the Collabora Online - Built-in CODE Server app, an optional component of Nextcloud, to gain unauthorized access to servers. The vulnerability allows attackers to plant web shells, which are small files that can execute commands sent by an attacker with the same privileges as the web server account. The issue was first reported by administrators on GitHub, with the initial attack occurring on September 10. The exploitation of this flaw enables attackers to send commands to the compromised server via web requests. The affected app is a built-in component of Nextcloud, specifically the Collabora Online - Built-in CODE Server.